Answer: 1260
Explanation:
The number of permutation of n things in which 'a' things are like , 'b' things are like and so on.. is given by :-

Given : A shipping company devises a messaging consisting of 9 flags hung in a line.
Then, the number of different possible messages constructed from a set of 4 white, 3 red, and 2 blue flags will be :-

Hence, the number of different possible messages constructed from a set of 4 white, 3 red, and 2 blue flags= 1260